This invention relates generally to apparatus for the electrostatic transfer of a developed image from a master to a receiving surface. More specifically, it pertains to the movable transfer means that contacts and traverses a carrier means which supports the master to effect the electrostatic transfer.
The permanent master and the transfer means are used repeatedly to produce high resolution and high quality images on receiving surfaces, such as printed circuit boards. Receiving surfaces, such as printed circuit boards, have traditionally been produced by individual laminating, exposing, developing, etching and stripping processes where dry film photoresist has been used to produce the conductive wiring patterns. Heretofore, there has been no method or apparatus available to produce a plurality of copies of conductive wiring patterns from a single master copy of the desired wiring pattern utilizing a dry film resist and photoimaging. There are many factors which prevented this type of a system from being employed to manufacture multiple copies from a single master.
Where liquid toner was employed, it was extremely difficult to attempt to clean excess toner or prevent the buildup of excess toner from the master. The ability to obtain a uniform and full width image over a large area, such as a 24 inch by 24 inch surface, was severely restricted. Trapped air or liquid solvent can frequently cause voids in the electrostatically transferred developed image. Where electrostatics were used to effect the transfer, the ability to separate the master surface and the receiving surface was critical and extremely difficult because of the electrostatic forces involved. Lastly, the availability of reliable and durable equipment to effect repeated transfers of the developed image on a master to a receiving surface was severely limited.
These problems are solved in the design of the apparatus of the present invention by providing transfer means that contacts the carrier of the master to effect an electrostatic transfer of a developed image to a receiving substrate by traversing the carrier means for a distance equal to at least the length of the master.